Darwinism and Neo-Darwinism

Darwinism

Charles Darwin was born in Shrewsbury, in Western England, in 1809. He joined the expedition on Beagle to the South American coastline. He observed and collected countless specimens of diverse fauna and flora of South America.

He observed that the animals and plants of the different regions of the continent had a definite South American stamp, very distinct from the life forms of Europe. Furthermore, the South American fossils that Darwin discovered, though different from modern species, were distinctly South American in their similarity to the living plants and animals of that continent.

The Galapagos Island

An especially puzzling case of geographical distribution was the animals of the Galapagos islands. The majority of the animal species on the Galapagos live nowhere else worldwide, although they resemble species residing on the South American mainland.

It was as though the islands were colonized by plants and animals that wandered off from the South American mainland and then diversified on the different islands. Amongst the birds, Darwin collected on the Galapagos were 13 kinds of finches that, although quite similar, appeared to be different species. Some were unique to specific islands, while other species were distributed on 2 or more islands that were close together.

After going back to Great Britain in 1836, Darwin viewed the origin of new species and adaptations as closely related processes. A new species would arise from an ancestral kind by the gradual accumulation of adaptations to different environments, separated from the initial habitat by geographical barriers. Over lots of generations, the two populations could end up being different adequate to be designated as different species. This is obviously what happened to the Galapagos finches.

Formulation of Darwin’s Theory

By the early 1840s, Darwin had worked out the significant features of his theory of natural selection as the system of adaptations. In 1844, Darwin wrote a long essay on the origin of species and natural selection.

However, before it could be published Alfred Wallace, a young biologist working in the East Indies established a theory of natural selection similar to Darwin’s. Wallace’s paper, along with extracts from Darwin’s unpublished 1844 essay, was presented to the Linnaean Society of London on July 1, 1858.

Darwin rapidly completed The Origin of Species and published it the next year. In this book, Darwin developed two main points:

1. Descent with Modification

Darwin believed in perceived unity in life, with all organisms related through descent from some typical ancestor that resided in the remote past. In the Darwinian view, the history of life resembles a tree, with multiple branching and rebranching from a common trunk to the tips of the living twigs, symbolic of the existing variety of organisms. At each fork of the evolutionary tree is a forefather common to all lines of evolutionary branching from that fork.

2. Natural Selection and Adaptation:

Darwin suggested that populations of individual species progress adapt to their regional environments through natural selection. Darwin’s theory of natural selection was based on the following observations.

1. The production of more individuals than the environment can support, results in a battle for existence amongst individuals of a population, with just a fraction of offspring surviving each generation.
2. Survival in the struggle for existence is not random but depends in part on the genetic constitution of the surviving individuals. Those individuals whose acquired qualities fit them finest to their environment are likely to leave more offspring than the fewer fit individuals.
3. This unequal capability of individuals to survive and replicate will result in a progressive change in a population, with beneficial attributes collecting over the generations hence leading to the evolution of a new species.

Neo-Darwinism – The modern evolutionary synthesis

The term Neo-Darwinism was first utilized in the 1880s by August Weismann, a German biologist, who integrated his theory of the germplasm into Darwin’s theory of evolution by natural selection. Neo-Darwinism, the modern-day variation of Charles Darwin’s theory of evolution by natural selection, integrates the laws of Mendelian genetics and emphasizes the role of natural selection as the main force of evolutionary modification.

The Origin of Species persuaded most biologists that species are products of evolution. A crucial turning point for evolutionary theory was the birth of population genetics, which emphasizes the comprehensive hereditary variation within populations and acknowledges the value of quantitative characters.

With progress in population genetics in the 1930s, Mendelism and Darwinism were reconciled, and the genetic basis of variation and natural selection was worked out. Therefore, a thorough theory of evolution that became known as the modern-day synthesis or Neo-Darwinism was developed. It is called a synthesis because it integrates discoveries and ideas from many different fields, including paleontology, taxonomy, biogeography, and population genetics.

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